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Biology Notes
Unit 1
1
...
The main forms are:
Coronary heart disease
Stroke
Diffusion:
‘’Movement of molecules or ions from a region of their high
concentration to a region of low concentration by relatively slow,
random movement of molecules
...
Substances are moved over
long distances by mass flow (all particles in a liquid move in one direction through tubes due to difference in
pressure)
...

Open circulatory system:
In insects, blood circulates in large open spaces
...

-

Higher blood pressure due to narrow channels instead of
large cavities
Blood travels faster
More efficient at delivering blood

The blood leaves the heart under high pressure, flowing along arteries,
arterioles then capillaries
...
Valves
ensure blood flows in one direction
...
Example of fish:

-

Heart pumps deoxygenated to the gills
Gaseous exchange takes place (diffusion of CO2 from the blood into water surrounding the gills and O2 from
water into the blood within the gills)
...

Double circulatory systems
Found in birds and mammals:
-

Right ventricle pumps deoxygenated blood to
the lungs where it receives oxygen
Oxygenated returns to the heart to be pumped a
second time (left ventricle) to the rest of the
body

The blood flows through the heart twice per circuit
...

-

Birds and mammals will have a high metabolic rate
Oxygen and food substances required for metabolic processes can be delivered quicker

The transport medium (blood)
All the particles the blood contains are transported in one direction due to a difference in pressure- mass flow
...

Cells such as red blood cells, white blood cells and platelets
Plays a role in the regulation of body temperature, transferring energy around the body
...
Dissolved substances can be transported around
organisms via the blood and lymph systems/ in plants through xylem and
phloem
...
The ions become hydrated in aqueous solution as they become surrounded by water molecules
...
g
...
These substances are hydrophilic
...
g
...
To be able to move around in blood, lipids
combine with proteins to form lipoproteins
...

Large input of energy caused little increase in temperature
Water warms up and cools down slowly
It’s very useful in organisms as it helps to avoid rapid changes in their internal temperature
Enables them to maintain steady temperature when surrounding temperature varies
Bodies of water won’t change rapidly
Water has a high boiling point due to many hydrogen bonds (lots of energy needed to break them)
...

Right side: deoxygenated blood from the body and pumps to lungs
Left side: oxygenated blood from lungs and pumps to body
The two sides are separated to prevent the mixing of the two types of
blood
...
Slow
flow allows exchange between blood and surrounding cells- network of capillaries are close to cells to ensure rapid
diffusion (smaller diffusion distance)
...
It has its own supply through coronary
circulation (coronary arteries, two capillaries and coronary veins)

The cardiac cycle
1
...


Ventricular systole

-

Slight delay
Ventricles contract from the base upwards
Pressure increases and opens semilunar valves

-

Blood flows through pulmonary arteries and
aorta
Pressure against atrioventricular valves closes
them, preventing backflow

3
...

The pressure has to be low to avoid damaging the lungs

Atherosclerosis
High blood pressure in arteries can cause damage to the walls
...

Summary:
-

Disease process leading to coronary heart disease and strokes
Fatty deposits block an artery or increase risk of being blocked by thrombosis (blood clot)
Blood supply can be blocked completely
Cells can be permanently damages
Coronary artery blockage = myocardial infarction
Arteries supplying the brain = stroke (damage/death of brain cells)
Narrowing leg arteries = tissue death = gangrene (decay)
Arteries can burst where blood builds up behind an artery that has been narrowed as a esult of
atherosclerosis

What happens in atherosclerosis?
1
...

3
...

5
...
White blood cells move into the artery wall, accumulating chemicals
from the blood (e
...
cholesterol)
...

Calcium salts and fibrous tissue build up, resulting in plaque on the inner wall (hard material)
...

Plaque causes the lumen of the artery to become narrower, making it harder to pump blood around the
body (rise in blood pressure
...


Blood clotting in arteries
It’s vital when vessels are damaged
...
When platelets (blood cell
with no nucleus) come into contact with a damaged blood vessel, they change from flat discs to spheres with thin,
long projections
...

They release a substance that activates more platelets
...
This
cascade of changes results in the formation of a blood clot
...

2
...

4
...

6
...

If endothelium is damaged, platelets come into
contact with exposed collagen
This triggers the cascade

Consequences of atherosclerosis
Angina is a chest pain caused by limited oxygen rich blood reaching the heart because of narrowed arteries
...
Blood supply can
be blocked completely so the heart muscle doesn’t receive any blood (ischaemic)
...
If the zone of dead
cells occupies a small area of tissue the
heart attack is less likely to prove fatal
...

All symptoms of a full stoke but
for less time
Full recovery is quicker
Could result in a full stroke in
the future
Blood clots blocking one of the arteries
leading to the brain, a full stroke will
result, Brain cells that are starved of oxygen for more than a few minutes will be permanently damaged- can be fatal
...
2 WHO IS AT RISK OF CARDIOVASCULAR DISEASE?
Risk is defined as the probability of occurrence of some unwanted event or outcome
...

Perception of risk
People overestimate risk of something happening if the risk is:
-

Not under their control
Not natural
Unfamiliar
Dreaded
Unfair
Very small

People underestimate familiar risks that
they think are under their control
...


People overestimate things where the consequences are sudden and severe and underestimate a risk is it
has an effect in the long term future (even if it’s severe)
...


Different types of risk factor
Lots of probabilities use figures for the whole population, giving averages that make the assumption that
everyone has the same chance of getting CVD for example
...

-

Age
Heredity
Physical environment
Social environment
Lifestyle and behaviour choices
Correlation and cause
Correlation: a change in one variable is
accompanied by a change in the other
-

Positive correlation is when an
increase in one = increase in the
other

-

Negative correlation is when an
increase in one = decrease in the
other

NOTE: large amounts of data are needed to ensure the correlation is statistically significant and it’s not just a chance
coincidence
...

-

Scientists try to carry out experiments with control variables, to see if altering one variable really does have
the predicted affect
...


1
...

COHORT STUDIES
-

-

Large group of people over time to see who develops the
disease
Prospective study- nobody at the start of the study has the
disease
Exposure to suspected risk factors/whether they develop
the disease is recorded so any correlations between risk
factors and disease development can be identified
Long time for the condition to develop
Studies can take years
Can be expensive

Cohort studies for CVD
Every two years,the participants are asked to provide a detailed medical history, undergo physical examination and
tests and answer questions about their lifestyle
...

CASE-CONTROL STUDIES
Case= group of people with a disease
Control= don’t have the disease
-

Retrospective study- information is collected about the risk factors that they have been exposed to in the
past, allowing factors that may have contributed to the development of the disease to be identified

-

control groups should be representative of the population
Controls can be matched to cases (e
...
age and sex similar
in the case and control group)
Variables that could be risk factors can’t be the factor
used to match the cases and controls

-

Case-control studies and CVD
-

Study results concluded 9 risk factors

-

Accounted for 90% of the risk
Same for men and women in almost every geographic
region and racial/ethnic group
Features of a good study

1
...


Representative sample

-

Selected from the wider population that conclusions will be applied to
Differences between people asked to take part in a study and those actually responding should also be
considered before generalising findings
Proportion of people who drop out of a study should be minimised (e specially in long studies e
...
cohort)
People who drop out often share common features

3
...


-

Similar results obtained when repeated with same equipment, procedure and conditions over a short timescale
Similar results obtained when used at different times, or by different people
Variables that can affect outcome have to be controlled, apart from the one investigated
Disease diagnosis must be clearly defined so other doctors can record and measure symptoms in the same way
...


Sample size

-

Large enough to produce results that can’t have occurred by chance
Large samples = more accurate estimates for the wider population

5
...
It may be due to arteries losing
elasticity and becoming more easily damaged due to ageing
...

-

Cuff wraps around upper arm
Manometer measures pressure

Cuff inflated- blood flow through the artery in the upper arm is stopped,
Cuff released- blood starts to flow through the artery
...

Its measured in millimetres of mercur mmHg (number of millimetres the
mercurressure will raise a column of mecury)
mecury)
...

Arteriols and capillaries have a greater surafce area than arteries, resisiting flow more sows blood down (lower
morepressure)
...

If smooth artery muscles contraac the vessel contricts,
contraact,
making the lumen narrower and increasing resistance
(blood pressure increases)
...

Factors that cause arteries/arterioles to ontrict:
-

Tissue fluid and oedema
Oedema is a sign of high blood pressure fluid building up in
pressuretissues and causing swelling
...


-

The blood contains plasma proteins giving the blood a relatively high solute potential (and therefore a low water
potential), tending to draw water into the blood
...
No blood cells or large
proteins leave as they are too big to fit through the gaps
...
Because of this, fluid drains back into the blood
...


-

About 90% of the fluid which leaks out of the capillaries seeps back in, the remaining 10% is returned to the
blood by the lymphatic system and is called lymph
...
These valves are large enough to allow proteins,
which are too big to get into the capillaries, into the lymph vessels
...


-

Blood consists of cells bathed in a liquid plasma
...
This is almost identical in composition to plasma but contains less protein molecules and no red blood
cells
...
Lymph is virtually identical in composition
to tissue fluid and just has a different name due to its different location
...

Calorie: 1000 calories (kilocalories)
Joule: unit of energy
Kilojoule: 1000 joules
4
...

1
...

Condensation- formation of complex molecules
Hydrolysis- splitting up a molecule with the addition of water

Monosaccharides
Single sugar units with the general formula (CH2O)n where n is the number of carbon atoms in the molecules
...

Glucose (alpha-glucose) and fructose are found naturally in fruit, vegetables and honey (used in cakes, biscuits and
other proper food)
...

Glycosidic bonds between two sugar units

White or brown crystalline sugar we use in cooking and the sugar in golden syrup is sucrose
Extracted from suar cane or sugar beet
Monosaccharides- rapidly absorbed into the blood- sharp ris ein blood pressure
Polsaccharides and disaccharides (complex carbohydrates)- digested into monosaccharides before absorbed so
theyre released slowly
Eating complex carbohydrates does not cause sudden swings in blood sugar
...
Asian and afro-caribbean people
have a high rate of lactose intolerance
...
This is carried out using the enzyme lactase which can be immobilised in
a gel, and milk is poured in a continuous stream through a column containing beads of the immobilised enzyme
...
Each sugar monomer is
joined to the chain in a condensation reaction with a water molecule release
...

-

Compact molecules
With low solubility in water

They don’t affect concentration of water in the
cytoplasm and so don’t affect movement of water in or out of cells by osmosis
...
Found in:
Fruit
Vegetables
Cereals
Can be used as a thickening agent when mixed with water and also added to many food products as a replacement of
fat
...

Composed of glucose molecules and stored in liver/muscles
...

Cellulose
Known as dietary fibre
...

-

Indigestible in the human gut
Responsible for movement of material in the digestive tract
Important in prevention of coronary heart disease, diabetes and bowel cancer

Lipids
General term for fats and oils
...
Theyre insoluble in water but soluble in organic solvents such as
ethanol
...
The bond beyween each fatty acid and glycerol is an ester bond (three ester bonds= triglyceride)
...

The chain is long and
straight
...

Animal fat from meat and
dairy are major sources of
saturated fats
...


Unsaturated fats
Monounsaturated: one C=C bond
in each fatty acid chain
Polyunsaturated: larger numbers
of double bonds
-

A double bond causes a kink in
the hydrocarbon chain

-

Kinks prevent chains packing
closely together

-

Increased distance = weaker
intermolecular foces = liquid oils
at room temperaature

-

Olive oil is high in
monounsaturated fat

-

Veg oils, nuts and fish are god
ources of polyunsaturated fats

-

Hydrogenated/Transfats:
Unsaturated fats can be made more solid by adding hydrogen to the double bonds- makes them saturated
...
Fat smust be present in a
balanced diet to avoid deficiency
...


Figures in table 1
...
4 which reflects
current activity levels of physical activity
...

BMR is higher in:
-

Males
Heavier people
Younger people
More active people

Eat fewerr kilojoules per day than used, you will have a
negative energy balance and energy stored in the body
will be used to meet the demand
...


Body mass index
-

Body mass (KG) divided by height
(m2)

-

Not very accurate- doesn’t take into
account muscle and fat levels in the
body

-

May not be accurate for athletes,
children, people over 60 and those
with long term health conditions
...
Narrowest point between the
rib margin and the top of the hip bone
Hip- light clothing
...


Non stretchable tape measure is used to attach to a spring scale with a tension of 750g
...
90
Women: shouldn’t be greater than 0
...

Low density lipoproteins:
-

Triglyceride from fat + cholesterol + protein = LDL
Transports cholesterol to body cells
Circulate in blood stream and bind to receptor sites on cell membranes
Taken up by cells where cholesterol is involved in synthesis and maintenance of cell membranes
Excess LDL overloads the membrane receptors = high blood cholesterol levels
LDL cholesterol may be deposited in the arter walls forming atheromas

High density lipoproteins:
-

Higher percentage of protein and less cholesterol compared to LDL (higher density)
Transport cholesterol from body tissue to the liver where its broken down
Lowers blood cholesterol and helps remove fatty plaques of atherosclerosis

People need a higher HDL:LDL ratio in the blood
...

Saturated fats may reduce activity of LDL receptors so LDLs arent removed- increasing CVD risk
Replacing saturated fat with polyunsaturated fat decreases both LDL and HDL levels- reducing LDL means
HDL:LDL ratio is increased (good)
...


Studies show theres no evidence for saturated fat contributing to coronary disease or polyunsaturated fats having a
protective effect
...
Transfats
shouldn’t exceed 2% of food energy so its not being used in foods anymore in the UK
...

Increased heart rate (to provide extra oxygen)

Nicotine in smoke stimulates adrenaline production
...

Chemicals in smoke damage linings in arteries, triggering atherosclerosis
...

Inactivity
Moderate exercise prevents high blood pressure and lowers it
Exercise maintains a healthy weight and raise HDL levels iwhtout affected LDL
Reduced chance of developing type II diabetes/ helps to control the condition
Heredity and risk
Some diseases are deternined by inheritance of a defective allele> However, some conditions that are controlled by a
single gene are known to depend on the different mutations that that gene, to determine how severe the condition is
...
Genes can be identified to not cause the condition directly but
still increase the individuals chance of developing it
...

Highly reative
Damage cell components (enzymes/genetic material)
Can develop cancer, heart disease or premature ageing
Mutations if DNA is damaged
Vitamin C, beta-carotene and vitami E provide hydrogen atoms that
stabilise the radical by pairing with its unpaired electron
...

Salt
Salt is needed for healthy functioning of your body
...
5 times
greater)
...

Stress
Poor stress management is linked to cornonary heart disease
...

Excess alcohol consumption can result in direct tissue damage
(e
...
liver, brain and heart)
...

2
...

Study: moderate alcohol consumption is correlated with higher HDL cholesterol levels
...
4 REDUCING THE RISKS OF CARDIOVASCULAR DISEASE
-

Stop smoking
Maintain restin g blood pressure below 140/85mmhg
Maintian low cholesterol
Maintianing normal BMI/low waist to hip ratio
Taking regular physical exercise
Moderate or no use of alcohol

Controlling blood pressure
Three types of drug needed for people with sustained systolic pressure of >160mmHg and diastolic pressure of
>100mmHg
1
...
This hormone causes constriction of blood
vessels to contol blood pressure
...


Calcium chnnel blockers
Antihypertensive drugs that block calcium channels in the muscle cells in the lining of arteries
...

Side effects:








Headaches
Dizziness
Swollen ankles (build up of fluid)
Abnormal heart beat
Flushing red in the face
Constipation

3
...
Gets rid of excess fluid and salt
...

Reducing blood cholesterol
One way to achieve this is through a low fat diet
...
Statins
Inhibit an enzyme involved in the production of LDL
cholesterol by the liver
Side effects:








Tiredness
Disturbed sleep
Feeling sick
Vomiting
Diarrhoea
Headache
Muscle weakness

They reduce the risk of heart idsease and stroke
...
People whoo have not had CVD but have elevated cholesterol leveles, statins lower total and LDL
cholesterol by more than 20% and the risk of CVD by a similar amount
...
g
...

Found in fruit, vegetables, beans, pulses and some grains
(e
...
oats)
...

First double bond between the third and fourth carbon atoms
Essential for cell functioning
Linked to reduction in heart disease and joint inflammation
More fruit and vegetables
Contain antioxidants and non-starch polysaccharides
...
g
...

Not effective for everyone
Atlernative platelet inhibitory drug: clopidogrel
Combination of aspirin and clopidogrel have a dramatic effect
RISK: bleeding in the gastrointestinal tract
:
Warfarin
Anticoagulant drug
Interferes of production of vitamin K
Stops the clotting process
Taken orally for extended periods of time

Use is suggested when the 10
10year risk of a heart attack of
stroke is greater than 20
20%

Aneurysm:
Artery bursting due to blood building up
behind a section of that artery that has
narrowed due to atherosclerosis

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